The present invention relates to a method and apparatus for cables used in a computer network system, and in particular to detecting proper or approved cables and reducing EMI.
Repeaters provided in computer or other networks, such as local area networks (LAN), wide area networks (WAN), telecommunications networks and the like, have typically been provided in monolithic or nondistributed fashion such as providing a single chassis or cabinet for a repeater to which the various signal sources/destinations are coupled e.g. via cables and the like. This configuration can be problematic when the space which is available for accommodating network equipment is limited and/or costly because the monolithic or undistributed repeater device will typically occupy a contiguous and relatively large portion of such space. The problem is exacerbated by the fact that repeaters (especially high-bandwidth repeaters such as repeaters configured for a bandwidth of 1 gigabit per second or more) are typically provided in substantially non-modular form, e.g. are available in a relatively few sizes (both in terms of physical size and the number of ports or connections supported). In such situations, it is impossible or infeasible for a user to be able to obtain a repeater of substantially the currently-required size. Typically, the user must employ a repeater which may be substantially larger and/or support more ports or connections, than actually required. Thus, the non-modular nature of typical repeaters means that more resources (both spatial and financial) are consumed, than necessary to achieve the required repeater functionality.
Another difficulty associated with the non-modular nature of previous repeaters is the inability to be readily reconfigured to accommodate changing conditions. For example, there may be network installations in which it would be desirable to facilitate expansion of the network e.g. as the number of users increases or other conditions change and/or to remove or isolate certain network components in other types of conditions. However, monolithic-type repeaters are included in one or a few discrete sizes on an xe2x80x9call or nothingxe2x80x9d basis. Thus, in a typical situation, a network may be configured with a repeater which is over-sized for current conditions, in anticipation of later growth, or as a result of user shrinkage.
Although it is desired to reduce the inflexibility in other disadvantageous aspects associated with undistributed and/or non-modular repeaters, it is preferred that such reduction in inflexibility should not entail an undue increase in the burden of installing, configuring or administering a network. Accordingly, it would be useful to provide a distributed and/or modular, preferably high bandwidth, repeater in which some or all features associated with installing, configuring, maintaining or administering the network are performed substantially automatically such as by automatically sensing installation or removal of repeater modules or module connections. In this regard, xe2x80x9cautomaticallyxe2x80x9d means substantially without the need for manual, human configuration or installation steps (such as setting switches and the like). For example, preferably repeater modules are readily installed or connected (e.g. by cables) by the end user in a relatively simple xe2x80x9cplug inxe2x80x9d fashion without the need for additional manipulation, such that the modules and/or associated circuitry sense the insertion, coupling or removal and perform appropriate configuration operations. Accordingly, it would be useful to provide a (preferably high-bandwidth) network repeater which is substantially distributed and/or modular in nature.
Yet another disadvantageous of nondistributed or non-modular repeaters is that malfunctioning or failed units cannot be readily isolated and/or replaced. Accordingly, it would be useful to provide a network repeater having a plurality of modules such that a failed or malfunctioning module can be readily detected, isolated, removed and/or replaced.
In situations where characteristics of components such as cables or other communication links can affect error rates or other performance features, of a repeater, proper operation of the overall system can be substantially influenced by the use (or lack thereof) of the proper type of cable or similar component. Accordingly it would be useful to provide a cable for use in an electronic system, including a distributed repeater system, configured to allow the system to sense whether a proper type of cable is coupled to the normally-used coupler and, preferably, taking appropriate action, in the system, such as suspending certain operations or providing a warning in the event of coupling an improper cable.
In numerous situations it is desirable to reduce or substantially eliminate electromagnetic interference from network devices (and other electronic devices), including cable connections therebetween. Accordingly, it would be useful to provide a cabling device or procedure for assisting in reducing or substantially eliminating electromagnetic interference associated with cable connections.
At least some aspects of the present invention include a recognition of problems in previous approaches, including problems as described herein. According to an aspect of the invention, a repeater is provided which is distributed in nature. xe2x80x9cRepeater,xe2x80x9d as used in the following, can include a device, function or process which may, in some circumstances, provide full-duplex communication (e.g. bypassing the repeater core) or may otherwise differ from prior usages of xe2x80x9crepeater.xe2x80x9d In one aspect the repeater function is performed by the combined operation of two or more, repeater modules which are spaced from one another and coupled together e.g. via cables. In one embodiment, different modules of the repeater may be housed in different network switches. For example, a computer network may include a plurality of switch boxes or chassis, typically all mounted in one or more racks, often adjacent one another with the switches being coupled to network nodes such as personal computers, work stations and the like. In one embodiment, two or more, in some cases, all, of the switches include one or more regions for receiving repeater modules, with the repeater modules in different switches being coupled to one another by cables and the like. Preferably, at least some aspects of system configuration are performed automatically. In one embodiment, the system will configure the distributed repeater to operate in full duplex mode (e.g. bypassing the repeater core) only if there are exactly two repeater modules coupled by a single (cable) link and otherwise (i.e. if there are three or more coupled repeater modules) the repeater will operate in half-duplex mode.
In one embodiment, a cable is configured to facilitate the system automatically detecting whether the cable, connecting one module to another, has an indicator indicating it is of an approved type and, preferably, the system will suspend or terminate transmissions if the cable does not include an indicator indicating it is of an approved type. In one embodiment, the indicator is other than a direct measurement of the characteristic-of-interest (i.e. a characteristic directly determining whether the cable is within desired or required performance parameters). For example, in one embodiment, the cables which are approved for use are marked by including a predetermined resistance between a specific pair of cable wires and the apparatus to which the cable is coupled includes circuitry for recognizing or detecting the presence or absence of such resistance between the predetermined pair of cable wires.
In one aspect of the invention, a repeater, useable for connecting switches in a data communication network, is provided in a distributed and/or modular fashion. The repeater includes a plurality of separate and distinct components or modules connected to or at least partially housed in, the various switches which the repeater modules couple. Preferably, the repeater autodetects and/or autoconfigures some or all aspects of repeater operations, such as detecting and/or configuring in response to appropriate or approved cable-type connections. The distributed and/or modular repeater facilitates accommodating various switching or repeater needs as a network grows or contracts. Preferably the cable couples are configured to reduce or avoid EMI. In one embodiment a conductive resilient O-ring is associated with a coupling, such as surrounding a sleeve of a cable coupler.